Buffer Status Reporting
In wireless communication systems, such as LTE, the uplink (as well as the downlink) transmissions are scheduled by the network. For LTE, as an example, this means that when and which resources a UE transmits on is indicated by the eNB including other information such as which modulation and coding scheme the UE shall apply, and so forth. For the eNB to be aware of how much resources to schedule the UE on the eNB would need to know how much data the UE has to transmit. For this purpose a buffer status reporting mechanisms is used in LTE according to which the UE sends MAC messages, referred to as MAC Control Elements, to the eNB indicating the size of the UE's uplink buffer.
FIG. 1 is a schematic diagram illustrating an example of buffer status reporting between a wireless communication device and a network node.
Section 5.4.5 of 3GPP TS 36.321 v12.5.0 relates to MAC operation and details the logic applied by a UE when determining when to send Buffer status Reports (BSRs).
WO 2015/047152 relates to a method for handling data transmissions in Long Term Evolution networks, and involves evaluating whether a trigger condition for buffer status reporting is fulfilled, and transmitting status report to radio base station when condition is fulfilled.
The 3GPP Draft; R2-080375, 20080108 3rd Generation Partnership Project (3GPP), Mobile Competence Centre; 650, route des Lucioles; F-06921 Sophia-Antipolis Cedex; France, RAN WG2, Sevilla, Spain; 20080108 discloses different triggers for buffer status reports.
Section 6.1.3.1 of 3GPP TS 36.321 v12.5.0 relates to MAC operation and details the definition of Buffer Status Reports (BSRs).
Pre-Scheduling for Latency Reduction
A way to reduce scheduling latency in LTE is to lower the time for grant acquisition by using various pre-scheduling or semi-persistent scheduling, SPS, strategies. The idea of pre-scheduling, which is supported already in Rel-8 as an implementation choice, is to opportunistically schedule users without scheduling request, SR, when network resources are available. With pre-scheduling, UEs can receive UL grants without the UE having sent, or the network having received, a prior request for an UL grant by the UE. A request could be for instance an SR and/or BSR. With SPS, the network can provide periodic UL grants and/or DL assignments with reduced L1/L2 control compared to dynamic scheduling. SPS can be used for pre-scheduling.
However, there is a general need for more efficient use of the available resources including optimized control signaling and/or increased channel occupancy and/or improved scheduling or resource allocation.